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16 SURFACEPREP 2015 COATINGSPROMAG.COM Concrete and Steel the best method — of protecting steel from corrosion. Applying coatings to large steel structures, such as bridges, water towers, and ships, is very expensive, so it is essential that the process be done properly to extend the life of the coating," said Azocar of Clemco. And proper surface prepa- ration is the best way to ensure that the coating system will stand the test of time. A lthough steel is a very diferent substrate from concrete, the two main components of the surface prepa- ration remain the same: cleaning and creating a proper surface, or anchor, profle. According to Chuck Lockard of Montipower, Inc., while coating surface preparation require- ments can vary between coatings, "the primary requirements are a level of 'cleanliness' — being free from corrosion, scale, and defunct coatings — and a degree of surface roughness, which is usually characterized by the depth of the micro-in- dentations in the substrate (profle or peak to valley depth) and the peak count (usually expressed as peak/cm)." NACE and SSPC ofer industry-wide joint and individ- ual standards for steel. Te degree of surface preparation required for a specifc job is determined by the existing condition of the steel and the coating material to be applied. From solvent cleaning to power-tool cleaning and aggressive abrasive blasting, the NACE and SSPC standards specifed on a project will assist coatings contractors in adhering to the appropriate surface preparation method. Contaminant Removal Clean steel is absolutely imperative to the proper adhesion of a coating system. If the surface is not cleaned properly, corrosion that remains from defcient cleaning can continue to develop beneath a new coating application and result in premature coating failure. Chemical or solvent cleaners can be used alone or in conjunction with other steel surface preparation methods depending on the required specif- cations and standards. HoldTight ofers one such product. According to Peter Petkas of HoldTight, this cleaner removes salt and fash rust. "Contaminants of any kind draw moisture to the surface of the steel, which can cause fash rust. HoldTight 102 leaves no residue behind, so there is nothing to separate the coating or liner system from the substrate. It is also non-hazardous, bio-degradable, and non-fammable," said Petkas. Tools of the Trade: Shot Blasters and Bristle Blasters Steel can have rust, mill scale, and coatings that need to be removed, and according to Rippman of Blastrac, this substrate requires far more impacts per square inch than concrete during the shot blasting process to achieve proper cleaning and profling. "We have a new product especially designed for steel substrates, such as petro-chemical and water tanks. Te Blastrac 900VMB is a vertical shot blasting system used in conjunction with a roof rigging system, winch, or crane to prepare the sides of vertical or near-vertical steel surfaces. Te 900VMB operates in an up-and-down direc- tion to clean and profle the surface and is guided via remote control," said Rippman. A nother sur face prep tool avai lable to applicators is the Br ist le Blaster. T his hand-held power tool removes contaminants and creates an anchor prof i le on steel by str ik ing the sur face w ith w ire br ist le belts. " T he Br ist le Blaster can deliver blast-qua lit y sur face preparation on steel sur faces w ithout the need for complex equipment or med ia recover y apparatus. It was developed extensively for use on pipelines, ref iner ies, br idge ref urbishment, Vertical surfaces need to be prepared properly as well. This is an example of a steel surface that's being profiled with a machine by Blastrac that's operated with remote control. There are several blasting options for steel substrates, including shot, bristle, and abrasive, which can help remove rust, mill scale, and coatings. Shown here is a wet abrasive blaster from Clemco.

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